Dynamic spin interchange in a tridentate Fe(iii) Schiff-base compound

Abstract

Dynamic spin interchange where crystals explode with preservation of magnetic memory is observed for a mononuclear hysteretic Fe(iii) Schiff-base compound.

Unusual Magneto‐Structural Features of the Halo‐Substituted Materials [FeIII(5‐X‐salMeen)2]Y: a Cooperative [HS‐HS]↔[HS‐LS] Spin Transition

“…[33] The object of this work is to revisit the [Fe III (X-salRen) 2 ]Y spin-crossover family [24,26] that originated in the 1970s and extend it with freshly designed members that have the potential to exhibit previously unobserved rare magnetic behaviour. In the course of this investigation, some aspects of our work coincided with the research conducted by Martinho et al [4,[31][32][33] Herein we present areport on as ystematic study of spin-crossover features within the series of halo-substituted complexes [Fe III (5-X-salMeen) 2 ]Y (X = F, Cl, Br and I; Y= ClO 4 and BPh 4 ). Previously,W ilson and Sinn along with their co-workers demonstrated magnetically and crystallographically the influence of electronic properties of substituent groups on thes pin states of the compounds in the series [Fe III (X-salMeen) 2 ]PF 6 (X = 5-OMe, 3-OMe and 5-NO 2 ).…”

“…The polymorph that crystallizes in the monoclinic space group P2 1 / c undergoes an abrupt complete S = 5/2$S = 1/2 crossover involvingo ne complex cation, [4] whereas the other polymorph which adopts the orthorhombic space group Pbcn is predominantly low spin at room temperature, and its incomplete spin crossover is characterizedb ya na symmetric hysteresis loop aroundr oom temperature. [32] The magneto-structural behaviour of the 5-iodo-substituted analogue has as triking resemblance to that of the latter polymorph, save for the irreversibility of the magnetic profilea nd the narrower hysteresis loop in this case. [33] The object of this work is to revisit the [Fe III (X-salRen) 2 ]Y spin-crossover family [24,26] that originated in the 1970s and extend it with freshly designed members that have the potential to exhibit previously unobserved rare magnetic behaviour.…”

“…Unfortunately, room‐temperature magnetic and crystallographic data on [Fe III (5‐Br‐ salEen) 2 ]Cl ⋅ 0.5 H 2 O are not available, nor a spin‐transition curve for this compound. [Fe III (5‐Br‐salEen) 2 ]ClO 4 exhibits polymorphism induced by the crystallization conditions. The polymorph that crystallizes in the monoclinic space group P 2 1 / c undergoes an abrupt complete S =5/2↔ S= 1/2 crossover involving one complex cation, whereas the other polymorph which adopts the orthorhombic space group Pbcn is predominantly low spin at room temperature, and its incomplete spin crossover is characterized by an asymmetric hysteresis loop around room temperature .…”

“…[Fe III (5‐Br‐salEen) 2 ]ClO 4 exhibits polymorphism induced by the crystallization conditions. The polymorph that crystallizes in the monoclinic space group P 2 1 / c undergoes an abrupt complete S =5/2↔ S= 1/2 crossover involving one complex cation, whereas the other polymorph which adopts the orthorhombic space group Pbcn is predominantly low spin at room temperature, and its incomplete spin crossover is characterized by an asymmetric hysteresis loop around room temperature . The magneto‐structural behaviour of the 5‐iodo‐substituted analogue has a striking resemblance to that of the latter polymorph, save for the irreversibility of the magnetic profile and the narrower hysteresis loop in this case…”

“…[29] Modulation of spin-crossover properties in iron(III)-salicylaldimine systemsb yi ntroducing halogen substituents into the para position of the phenolate moiety has been demonstrated spectacularly by the complexes [Fe(qsal-5-X) 2 ]Y (qsal = quinolylsalicylaldiminate;X = halogen;Y = counter anion). [6,7,11,18,30] Within the family [Fe III (R 1 ,R 2 -salRen) 2 ]Y,o nly three crystallographically characterized 5-halo-substituted members are known,n amely [Fe III (5-Br-salEen) 2 ]Cl·0.5 H 2 O, [31] [Fe III (5-Br-salEen) 2 ]ClO 4 [4,32] and [Fe III (5-I-salEen) 2 ]ClO 4 . [33] [Fe III (5-Br-salEen) 2 ]Cl·0.5 H 2 Oe xists at 150 Ka st wo independent complex cations in the crystallographic asymmetricu nit:o ne in the HS state and the other in the LS state, am agnetic feature not crystallographically observed previously in this system.…”